What causes "SR.GlyphsCaretStopsContainsHexDigits" in dotnet/wpf?

Replace every non-hex character in the CaretStops string with a valid hex digit

dotnet/wpf · error · ArgumentException

SR.GlyphsCaretStopsContainsHexDigits

Error message

SR.GlyphsCaretStopsContainsHexDigits

What it means

Glyphs.ParseCaretStops validates the CaretStops string, which must contain only hex digits (0-9, a-f, A-F). Any other character makes the caret-stop bitmap unparseable, so an ArgumentException is thrown naming the CaretStops property.

Solutions

Replace every non-hex character in the CaretStops string with a valid hex digit
Remove separators/spaces between hex groups
Validate the string with a regex before assigning it

Example fix

// before
CaretStops = "00F0 0FF0";
// after
CaretStops = "00F00FF0";

Defensive patterns

Strategy: validation

Validate before calling

bool ok = string.IsNullOrEmpty(caretStops) || System.Text.RegularExpressions.Regex.IsMatch(caretStops, "^[0-9a-fA-F]*$");
if (!ok) throw new ArgumentException("CaretStops must be hex digits only");

Try / catch

try { glyphs.CaretStops = value; } catch (ArgumentException) { /* sanitize to hex and retry */ }

Prevention

Regex-validate hex-only before assignment
Never insert spaces/commas into CaretStops
Build CaretStops with string.Format("{0:X}", bits) style code

When it happens

Trigger: Setting Glyphs.CaretStops (typically via XAML) to a string containing a non-hex character, e.g. spaces, 'g'-'z', punctuation, or sign characters.

Common situations: Hand-edited XAML where CaretStops was typo'd; programmatic string building that inserted separators like commas or spaces between hex groups.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/ea224566d992dd26. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Documents/Glyphs.cs:248

            bool[] caretStops = new bool[caretStopCount];

            int i = 0;
            foreach (char c in caretStopsString)
            {
                if (Char.IsWhiteSpace(c))
                    continue;

                int nibble;

                if ('0' <= c && c <= '9')
                    nibble = c - '0';
                else if ('a' <= c && c <= 'f')
                    nibble = c - 'a' + 10;
                else if ('A' <= c && c <= 'F')
                    nibble = c - 'A' + 10;
                else
                    throw new ArgumentException(SR.GlyphsCaretStopsContainsHexDigits, "CaretStops");

                Debug.Assert(0 <= nibble && nibble <= 15);

                if ((nibble & 8) != 0)
                {
                    if (i >= caretStops.Length)
                        throw new ArgumentException(SR.GlyphsCaretStopsLengthCorrespondsToUnicodeString, "CaretStops");
                    caretStops[i] = true;
                }
                ++i;
                if ((nibble & 4) != 0)
                {
                    if (i >= caretStops.Length)
                        throw new ArgumentException(SR.GlyphsCaretStopsLengthCorrespondsToUnicodeString, "CaretStops");
                    caretStops[i] = true;
                }
                ++i;
                if ((nibble & 2) != 0)

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